Apparatus for forming seamless tooth-crowns.



' No. 690,085. Patented Dec. 3|, |90|.

' ,1. F. TWIST.

APPARATUS FOR FORMING SEA MLESS TOOTH GROWNS.

(Apphcation filed Mar. 2, 1901.)

(No Model.)

UNTTFD STATES PATENT JOSEPH FRANKLIN TWIST, OF SAN FRANCISCO, CALIFORNIA.

APPARATUS FOR FORNHNG SEAM LESS TOOTH-CROWNS.

SPECIFICATION forming part Of Letters Patent No. 690,08 5, dated December 31, 1901.

Application filed March 2, 1901. Serial No. 49,570. (No model.)

To all whom it may concern:

Be it known that I, JOSEPH FRANKLIN TWIST, a citizen of the United States, residing in the city and county of San Francisco, State of California, have invented an Improvement in Apparatus for forming Seamless Tooth- Crowns; and I hereby declare the following to be a full, clear, and exact description of the same.

My invention relates to an apparatus which is especially designed for the manufacture and shaping of tooth-crowns which are made of seamless metal.

It consists particularly in devices substantially set forth in the claims for formin the male and female members of a die which is the counterpart of the completed crown and a means for fitting the cap between the parts of the die and applying pressure thereto t give itthe eXact desired shape.

It also comprises details of construction, which will be more fully explained by reference to the accompanying drawings, in which- Figure 1 is a perspective view of a moldingflask, showing the cast A in place. Fig. 2 is a view of the die 5. Fig. 3 represents the two parts of the cast. Fig. 4: is a sectional view of a mechanism for compressing the parts and shaping the crown.

What are known as seamless toothc'rowns are formed from caps of thin metal, such as gold, these caps being made in a cylindrical form, with one closed end, by forcing disks of metal through dies of gradually-decreasing diameter by means of punches suitably constructed for the purpose. These caps of various sizes are kept in stock and are used for making tootlrcrowns of any size which may be desired.

In my invention I first obtain the shape of the desired crown by the application of plastic material to the tooth or by other suitable or well-known means, which it is not necessary to here describe. This shape then forms a mold, from which a plaster or similar cast is made, the end of which is the exact form of the proposed crown when completed. This cast or pattern, which is shown at A, is then pressed into a body of moldine or other suitable plastic material which is contained in one-half of a molding-flask 2 of any suitable or desired form. The moldine is placed in one-half of the flask 2 and the plaster cast is pressed into the moldine, so as to be approximately about half embedded therein. The flask is then closed and type or other hard metal which has been melted is poured into the other half of the flask, thus fitting and inclosing the projecting half of the plaster cast A. hen cold, the flask is opened, the moldine is removed from the half which it filled, and the plaster cast is left half embedded in the metal which fills the other half of the flask, the flask being again closed after suitably preparing the surfaces so that they will not stick together. The now empty half is filled with the same hard metal and the plaster cast is embedded in the two halves 3 3. When cold, the flask is opened, the plaster cast taken out, and I then have a complete intaglio metal impression of the tooth-crown to be made. This forms the female member of the die to beused. The flask 2 is preferably made concave in the lower end and may be also slightly tapered or cone-shaped, as shown, so that when the cast 3 3 of the two halves of metalhave been made they will when removed have a convex end 4;, and this end is open by reason of the plaster cast having been so embedded as to project through that end of the casting. After this hard-metal mold has been completed it is suitably coated to prevent adhesion, and it then serves as a mold into which a soft fusible metal is poured, and this makes a die 5 exactly the same shape as the original plaster cast and the interior of the mold. This being completed, a gold cap 6, formed as previously described, is selected which will fit upon the fusible metal die, and this is partly shaped by trimming and rubbing or sandpaper finish. This fusiblemetal interior die, with the cap upon it, is then placed within the corresponding hollow or exterior die, consisting of the parts 3 3. The hardmetal exterior die, consisting of the parts 3 3, is then placed in a cup 7, the interior of which is. shaped similarly to the exterior of the die 3 3. The exterior of the cup is screw-threaded, and a correspondinglythreaded sleeve 8 is fitted over it. This sleeve has means for attaching a lover or wrench by which it can be turned. As here shown, it has upwardly-projecting lugs 9, and the lever has corresponding holes which fit over the lugs, and by turning the lever 10 the sleeve is screwed down upon the part 7. Before this is done I place a plunger 11 in the cup 7, resting it upon the top of the hard-metal twopart die 3 3. The lower end of the plunger is made concave, as shown, and fits the 'corresponding convex surface of the die 3 and the upper end of the interior or male member 5 of the die upon which the gold cap was fitted. The concaved face-plungeris preferably made with a stem 14, which projects out through a hole in the top of the screw-threaded sleeve, and this serves as a guide to keep it in position. The threaded sleeve being 'then screwed down upon the cup the male and female members of the die are closely compressed, and the gold cap between them is thus given the shape desired, and by reason of the interior and exterior surfaces being fitted to corresponding shapes no pressure can occur which will distort the finished tooth-crown. After it has been sufficiently pressed and shaped the screw-sleeve is removed and the die taken out of the cup part, separated, and the crown can be removed by melting outthe interior fusible-metal die or by the usual means, and the crown is then in condition for use.

By this device the crown may be compressed into any desired form, such as a concave or depressed front, so that a porcelain front can be applied or other like or irregular form.

Having thus described myinvention, what I claim as new, and desire to secure by Letters Patent, is-- 1. A device for forming seamless toothcrowns, consisting of an interior die having the shape of both the cusp and lateral surfaces of the crown upon which the crown is fitted, an exterior two-part female die of the same shape within which the male member and tooth-crown are placed, and a mechanism by which the parts are compressed together and the crown is shaped to conform therewith.

2. A device for forming seamless toothcrowns, consisting of a male and female die having the shape of both the cusp and lateral surfaces to be given to the crown after the cap from which the crown to be formed has been placed upon the male member, and the latter inclosed within the female member of the die, a cup, the interior of which is fitted to receive the exterior of the outer die, a plunger having the lower end fitted to the top of the die, and means for applying pressure to said plunger whereby the crown is compressed between the outer and inner portions of the die.

3. A device for forming seamless toothcrowns, consisting of a die composed of male and female members between which the crown is fitted, said members each having the shape of both the cusp and lateral surfaces of the crown, a cup having screw-threads upon the outside, and the interior adapted to receive the outer die, a plunger having a coneaved face fitting the corresponding top of the die, and a central upwardly-projecting stem, and a sleeve screw-threaded to fit the threads of the cup, having a closed top with central guide-opening for the stem of the plunger, and projecting lugs.

4. A device for the formation of seamless tooth-crowns, consisting of a two-part female die of hardmetal formed successively about a plaster cast of the tooth-crown, and a male interior die of soft metal formed by casting it within the completed female die, said dies having the shape of both the cusp and lateral surfaces of the crown, and forming a matrix between which the cap is placed from which to form a tooth-crown, and a mechanism for compressing the dies together whereby the crown is shaped.

In witness whereof I have hereunto set my hand.

JOSEPH FRANKLIN TWIST.

Witnesses:

S. H. NOURSE, JESSIE O. BRODIE. 

